Browse Prior Art Database

Synchronous Stacker Servo

IP.com Disclosure Number: IPCOM000109881D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 3 page(s) / 174K

Publishing Venue

IBM

Related People

Call, MG: AUTHOR [+3]

Abstract

A continuous forms stacker is typically fed by tractors which are gear linked to the folding mechanisms and provide the synchronization of the mechanisms to paper perforations which are initially aligned in the tractors. Folding mechanisms consist of the stacking head and a chute which guides the paper into it. A folding/stacking mechanism which avoids the necessity for a separate tractor and corresponding paper alignment, mechanical adjustment and change of links and gears when form size is changed is described. The printer in which this stacker is incorporated has a vacuum column-type paper buffer, called the output buffer, between the transfer station tractors and the stacker to provide paper transport tension through the transfer station and fuser, and to buffer tractor motion from the stacker.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 40% of the total text.

Synchronous Stacker Servo

       A continuous forms stacker is typically fed by tractors
which are gear linked to the folding mechanisms and provide the
synchronization of the mechanisms to paper perforations which are
initially aligned in the tractors.  Folding mechanisms consist of the
stacking head and a chute which guides the paper into it.  A
folding/stacking mechanism which avoids the necessity for a separate
tractor and corresponding paper alignment, mechanical adjustment and
change of links and gears when form size is changed is described.
The printer in which this stacker is incorporated has a vacuum
column-type paper buffer, called the output buffer, between the
transfer station tractors and the stacker to provide paper transport
tension through the transfer station and fuser, and to buffer tractor
motion from the stacker.  The stacker head and paper chute are
independently servo-controlled and synchronized to the paper
perforations fed from the output buffer.  Paper position information
for synchronizing the stacker comes from the output buffer roll of
the vacuum column and tractors, allowing servos to automatically
align perforations in the stacker, and to handle all the ratio
adjustments based on fold length.

      A diagram of the stacker head servo is shown in the figure.
This figure also shows chute-positioning control.

      The position encoder of the output buffer roll has an error
which accumulates over time as the roll moves paper because the roll
is not tractor-geared to the paper.  This error is corrected by
comparing the output roll encoder to the tractor encoder when the
paper path length between these two mechanisms is a known fixed
value.  The output roll servos the position of the loop of paper in
the vacuum column to a sensor in the column; however, large
excursions away from this sensor can occur.  The encoder correction
is done at the moment the paper loop crosses this sensor.

      The correction counter counts the difference in output roll
encoder pulses and tractor encoder pulses by incrementing on roll
pulses and decrementing on tractor pulses for forward paper motion at
these encoders, and vice-versa for backward paper motion.  Beginning
with a value of zero, when the paper loop in the vacuum columns is at
the servo sensor, this counter would always have the value zero when
the loop returns to the servo sensor if the output roll encoder has
no error.  This result indicates simply that the output roll has
removed just as much paper as the tractor has fed into the column.  A
non-zero value is the error in the output roll encoder with respect
to the tractor encoder, and this number is used to correct the roll
encoder.  The output roll encoder feeds several up-down counters, and
correction is accomplished by clocking these counters either up or
down by the number and sign provided by the correction counter.  The
correction counter is also clocked by the same process to zero its
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